1971 Impala

[Morbid]

Okay car buffs, got a question for ya's.

So up the road from me, there is a man who has what I believe to be a 1971 Chevy Impala.  I was going to stop and take a look at it, to see if it's worth buying as I was kinda interested in it.  Problem is, he's asking $4,500 OBO, which I'm not 100% sure what a fair price would be for it.  As I've not looked at it as of yet, I've no idea what the interior looks like, but I know it runs - I've seen him drive it - how well though not sure.  When I take a look probably tomorrow, I'll be able to provide more details.  What're some stuff I should be looking for?